Taken from upstream commit 42f6c72caa7294d5f357e790205b9569b8775f47.

diff --git a/src/attrs.rs b/src/attrs.rs
index b59aa2ee..1f4eaaca 100644
--- a/src/attrs.rs
+++ b/src/attrs.rs
@@ -19,7 +19,7 @@ use crate::{
 
 use std::env;
 
-use heck::{CamelCase, KebabCase, MixedCase, ShoutySnakeCase, SnakeCase};
+use heck::{ToKebabCase, ToLowerCamelCase, ToShoutySnakeCase, ToSnakeCase, ToUpperCamelCase};
 use proc_macro2::{self, Span, TokenStream};
 use proc_macro_error::abort;
 use quote::{quote, quote_spanned, ToTokens};
@@ -842,7 +842,7 @@ impl CasingStyle {
     fn from_lit(name: LitStr) -> Sp<Self> {
         use self::CasingStyle::*;
 
-        let normalized = name.value().to_camel_case().to_lowercase();
+        let normalized = name.value().to_upper_camel_case().to_lowercase();
         let cs = |kind| Sp::new(kind, name.span());
 
         match normalized.as_ref() {
@@ -874,9 +874,9 @@ impl Name {
             Name::Derived(ident) => {
                 let s = ident.unraw().to_string();
                 let s = match style {
-                    Pascal => s.to_camel_case(),
+                    Pascal => s.to_upper_camel_case(),
                     Kebab => s.to_kebab_case(),
-                    Camel => s.to_mixed_case(),
+                    Camel => s.to_lower_camel_case(),
                     ScreamingSnake => s.to_shouty_snake_case(),
                     Snake => s.to_snake_case(),
                     Lower => s.to_snake_case().replace("_", ""),
@@ -896,9 +896,9 @@ impl Name {
             Name::Derived(ident) => {
                 let s = ident.unraw().to_string();
                 let s = match style {
-                    Pascal => s.to_camel_case(),
+                    Pascal => s.to_upper_camel_case(),
                     Kebab => s.to_kebab_case(),
-                    Camel => s.to_mixed_case(),
+                    Camel => s.to_lower_camel_case(),
                     ScreamingSnake => s.to_shouty_snake_case(),
                     Snake => s.to_snake_case(),
                     Lower => s.to_snake_case(),
